Rheological Property of Composite Lithium Based Magnetorheological Grease Based on Poly-alpha Olefin Synthetic Base Oil

Composite lithium-based magnetorheological greases, containing 30wt%, 45wt%, 60wt% ferromagnetic particles, respectively, were prepared by using PAO40 poly-alpha olefin synthetic base oil, thickening agents of dodecyl hydroxyl stearic acid, sebacic acid, boric acid and lithium hydroxide, and FeSiB soft magnetic powder. The rheological property and magnetorheological effect of the magnetorheological greases were studied. The results show that the shear stresses of the three magnetorheological greases increased with increasing shear rate, and increased rapidly and then tended to be stable with increasing current. The storage modulus decrased rapidly and then tended to be stable with increasing shear rate, and increased first and then tended to be stable with increasing current. With increasing current, the loss factor of the magnetorheological grease increased first, then decreased and then tended to be stable, the damping characteristics and the magnetorheological effect were improved. The higher the ferromagnetic particle content, the larger the shear stress and the storage modulus of the magnetorheological grease, and the stronger the damping characteristics and the magnetorheological effect.